(1) Field of the Invention
The present invention relates to a method of and apparatus for detecting microorganisms. More particularly, it relates to a microorganism detecting method and apparatus for measuring microorganisms contained in a microorganism sample such as a sample in which the microorganisms of an object to-be-inspected are caught on a membrane filter and then subjected to fluorescent staining.
(2) Description of the Related Art
Heretofore, microbial tests in, for example, the manufacturing process managements and product quality controls of drinkables such as beer, edibles, pharmaceuticals, cosmetics etc. have been conducted in accordance with cultural tests requiring multifarious culture grounds, and long days have been expended till the ends of the tests. Therefore, test results such as the presence of microorganisms and the numbers of microorganisms have been known late, and there have been many limitations at the stages of researches, developments, manufactures and product shipments in various fields.
In view of such circumstances, a large number of rapid measurement methods have heretofore been devised (Misao HARUTA, et al., Simplification, Automation and Speed-up of Food-microbiological Tests, p. 11, Science Forum (1985), and Toshiki MORICHI, New Food Industry, 30, 49 (1989)), but satisfactory methods or apparatuses have not been developed yet. There have been developed, for example, an ATP measurement method (Molin, O., Milsson, L. and Ansehn, S., J. Clin. Microbiol., 18, 521 (1983)), an impedance method (Brown, D., Warner, M., Taylor, C. and Warren, R., J. Clin. Pathol., 37, 65-69 (1984)), an enzyme/fluorescence detecting method (Japanese Patent Laid-open Pub. No. 116700/1983), and a DEFT method in which a membrane filter method and a fluorescence microscope method are combined (G. L. PETTIPHER, UBALDINAM and RODRIGUES, J. Appl. Bacteriol., 53, 323 (1982)), and apparatuses to which these principles are applied are commercially available. However, problems are still left in points of accuracy and rapidity. More specifically, the rapid measurement methods presently in practical use exhibit, at the utmost, accuracies of 10.sup.2 -10.sup.4 microorganisms/ml. One day is usually required for one microrganism to reach this germ density. Another difficulty is that the running costs of culture grounds, reagents etc. are high.
Recently, an apparatus wherein microorganisms are automatically detected rapidly by a fluorescence detecting method subjecting the microorganisms to fluorescent staining has been proposed (Japanese Patent Laid-open Pub. No. 53447/1988), and it is studied to put the apparatus into practical use as ones of higher rapidity. Since, however, microscopic foreign matters having auto-fluorecences exist in large numbers in the natural world, the apparatuses simultaneously detect the auto-fluorescent foreign matters other than the fluorescent-stained microorganisms. Consequently, in the test of microorganisms contained in a sample to-be-inspected, for example, a product such as beer or any other drink, there is left the problem that the final decision cannot held being relied on a verification based on a visual inspection with a fluorescence microscope section. Accordingly, it is the most important theme to solve the problem in the automation of the microorganism detection based on the fluorescence detecting method.